Dialkyl ethers are known to be useful as diesel fuel cetane enhancers. For example published patent application WO2001/018154 discloses a diesel fuel formulation comprising dibutyl ether. Dibutyl ethers may be produced from butanol and the reaction is generally carried out via the dehydration of n-butyl alcohol by sulfuric acid, or by catalytic dehydration over ferric chloride, copper sulfate, silica, or silica-alumina at high temperatures (see for example, Karas, L. and Piel, W. J., Ethers, in Kirk-Othmer Encyclopedia of Chemical Technology, Fifth Ed., Vol. 10, Section 5.3, p. 576).
It is widely known that ethanol can be recovered from a number of sources, including synthetic and fermentation feedstocks. Methods for producing 1-butanol from ethanol are known as well. It is also known that 1-butanol can be prepared by condensation from ethanol over basic catalysts at high temperature using the so-called “Guerbet Reaction” (see for example, J. Logsdon in Kirk-Othmer Encyclopedia of Chemical Technology, John Wiley and Sons, Inc., New York, 2001). The production of transportation fuels from ethanol is widely accepted in the gasoline market; however the production of diesel fuel or fuel additives from ethanol has not been described. In addition, dialkyl ethers derived from ethanol can provide an advantage over petroleum based diesel and vegetable or animal fat based diesel in the reduction of greenhouse gas emissions and reducing reliance on scarce petroleum reserves.
The production of dibutyl ethers from butanol has been described in the prior art, however, the process for making these dibutyl ethers from butanol and other alcohols synthesized from ethanol over a base catalyst has not been described. The present invention provides a route to a dialkyl ether composition comprising a mixture of dialkyl ethers useful as a fuel additive providing an alternative to traditional petroleum sources.